With the ongoing trend towards smaller, faster and higher performance electrical components, such as a processor used in computers, routers, switches, etc., it has become increasingly important for the electrical interfaces along the electrical path to also operate at higher frequencies and at higher densities with increased throughput.
In a traditional approach for interconnecting circuit boards, one circuit board serves as a backplane and the other as a daughter board. The backplane typically has a connector, commonly referred to as a header that includes a plurality of signal pins or contacts, which connect to conductive traces on the backplane. The daughter board connector, commonly referred to as a receptacle, also includes a plurality of contacts or pins. Typically, the receptacle is a right angle connector that interconnects the backplane with the daughter board so that signals can be routed between the two. The right angle connector typically includes a mating face that receives the plurality of signal pins from the header on the backplane and a mounting face that connect to the daughter board. Likewise, the header comprises a mating face adapted to mate with the mating face of the right angle connector and a mounting face that connects to the backplane board.
As the transmission frequencies of signals through these connectors increase, it becomes more desirable to maintain a desired impedance through the connector to minimize signal degradation. A ground shield is sometimes provided on the module to reduce interference or crosstalk. In addition, a ground shield may be added to the ground contacts on the header connector. Improving connector performance and increasing contact density to increase signal carrying capacity without increasing the size of the connectors is challenging.
Some older connectors, which are still in use today, operate at speeds of one gigabit per second or less. In contrast, many of today's high performance connectors are capable of operating at speeds of up to 10 gigabits or more per second. As would be expected, the higher performance connector also comes with a higher cost.
When trying to design an electrical connector having a reduced pitch between signal pins, so as to obtain an electrical connector with a reduced size or with an increased pin density, the signal pins are made thinner and are therefore more fragile and likely to be bent or broken. When these electrical connectors are implemented in high-speed applications involving high transmission data rates, it is crucial to guarantee a high degree of electrical performance. However, the impedance and other important electrical properties of an electrical connector are dependent on the geometrical arrangement of the signal pins with respect to one another. Hence, it is challenging to design an electrical connector having a smaller pitch between its contacts, while guaranteeing high electrical performance.
Another problem, which might occur in electrical connectors, is that the contacts in the housing of the electrical connector, in particular the resilient parts that are located at the end of the electrical contacts, may be inaccurately positioned. This inaccurate positioning is considered a failure mechanism according to the electrical connector qualification tests used for telecommunication connectors such as Telcordia GR-1217-Core in the American market. This inaccurate positioning of the resilient part of the electrical contacts within one electrical connector can occur during production, handling, insertion, board handling, mating, etc. Furthermore, interferences may result that cause deviations from the contact normal force that has been originally designed. Moreover, the contact normal force may also decay with time due to stress relaxation or deformations of the resilient parts of the electrical contacts or deformations of the plastic connector parts of the housing. If the contact normal force is reduced to low levels, any additional decrease could be unacceptable and the contact normal force may reach critical minimum values.
An impedance matched backplane connector is disclosed in European patent EP 0 422 785 B1, wherein an electrical connection system includes a plurality of housing modules, each of the modules including a front mating face having a plurality of pin receiving passageways. In order to assemble the connector assembly, a plurality of terminal subassemblies is foreseen, each terminal subassembly being inserted into the rear of the housing modules, such that the terminal subassemblies are each stacked one against the other. The terminal subassemblies comprise electrical contacts in the form of blade sections that, when the terminal subassemblies are inserted into the housing modules, are aligned with vertical slots arranged in the rear of the housing modules, thereby disposing the plurality of opposed contact portions of the terminal lead frames adjacent to the narrow aperture at the front mating face of the connector.
However, in the connector assembly disclosed in the European patent mentioned above, the electrical contacts within the male electrical connector are not fully supported. Hence, in the case of thin electrical contacts, which are more fragile, and may thus break easily, the electrical connector is not very reliable and has a relatively short lifetime. Furthermore, the female connector disclosed therein is based on a double-beam contact principle, i.e. two female contacts mating with one male electrical contact. Such a two-contact female connector interface however presents the technical drawback that the contact normal force is often reduced to critical minimum values.
Other contact failure mechanisms involved in electrical connector designs in the art is the deposition of dust or particulates on contact surfaces, connector wear or gaseous corrosion of exposed non-noble metals out of which the contacts may be made.